Enameling furnace



Nov. 23, 1937. J. l.. MCFARLAND ENAMELING FURNACE Filed sept. 23, 195e Patented Nov. 23, 1937 ENAMELING FURNACE James L. McFarland, Schenectady, N. Y., assignor to General Electric Company, a corporation of New York Application September 23, 1936, Serial No. 102,152

6 Claims.

My invention relates to furnaces through which the material to be heated is moved in a continuous manner and particularly to furnaces for the continuous ring of enameled ware.y

One object of my invention is to provide an improved furnace of this character having means whereby enameled ware comprising large and heavy articles may be supported for movement through the furnace without danger of the articles being warped or distorted in form due to their weight and Without danger of dirt or other matter falling on the ware from the supporting means during its movement through the furnace. Another object is to provide a furnace of double decked form in which there may be a rapid transfer of heat from hot ware on one deck to cool ware on the other deck without any danger of dirt or other matter falling from the upper deck upon the ware on the lower deck. A further object of my invention'is the provision of an improved furnace of this character wherein the ware in moving through the furnace passes through different atmospheres, a relatively sharp line of division being preserved between the atmospheres.

My invention will be better understood from the following description taken in connection with the accompanying drawing, and its scope will be pointed out in the appended claims.

Referring to the drawing Fig. 1 is a vertical longitudinal sectional view of an enameling furnace embodying my invention; Fig. 2 is a crosssectional view taken on the line 2-2 of Fig. 1 but drawn to a larger scale; and Fig. 3 is a crosssectional View thereof taken on the line 3 3 of Fig. 1 also drawn to a larger scale.

The furnace comprising my invention has a steel framework formed, for example, of the structuralsteel members I and 2 and the encloing steel casing 3 which is more clearly shown in the enlarged cross-sectional views 2 and 3. Within the casing 3 is the heat insulating material 4 having the lining 5 of suitable refractory material. Two chambers arranged one above the other are thereby formed through which the ware which has previously been coated with vitreous enamel is carried with a uniform movement from one end of the furnace to the other, the material in one chamber being moved in a direction opposite to that of the other chamber. If desired, the furnace may be constructed with the chambers or at least the central portions thereof extending horizontally; however, l.' pre` fer to have the two chambers inclined downwardly from an intermediate high point or peak which -ployed in enameling furnaces for the reason is Asubstantially midway of the two ends of the furnace whereby there may be less heat lost from the open ends of the furnace and better control of the atmospheres in the furnace may be had. 'I'he furnace may be regarded as having three 5 sections, the central or main heating and ring section A which is provided with heating apparatus and the two adjoining end or heat exchange sections B where the cool ware in entering the furnace is preheated by receiving heat from the ware which is about to leave the furnace.

The upper and lower chambers of the central section A are separated from each other by the arch 'I of refractory material forming the roof of the lower chamber and the floor of the upper chamber. In the end sections B the upper and lower chambers are separated by the baie 8 which, as more clearly shown in Fig. 2, comprises the central plate 9 and the two side plates I0. Plate 9 is mounted somewhat above the side 20 plates I 0 and overlaps the adjacent edges of those plates. Plates I0 are spaced somewhat from the*J side Walls of the furnace, the two sets of plates being supported on cross members I I. The purpose of this baille construction is to prevent dirt and other material from falling from the upper chamber onto the ware in the lower chamber, but still allow the free passage of the surrounding atmosphere from vone chamber to the other and hence the rapid exchange of heat between the chambers.

While the enameling furnace which I have devised is adapted for use for firing vitreous enamelware of various sizes, it is constructed primarily for handling pressed steel sanitary ware of large size, such for example as bath tubs, illustrated at I2 on the drawing. Difliculty has been l experienced in supporting ware of this character by the overhead carrier means heretofore emthat the great weight of the ware has often resulted in the ware becoming warped when hung by a supporting structure. Another difficulty has been that due to dirt and other material falling upon the ware from the overhead supporting mechanism before the enamel has become hard.

I avoid these diniculties in the furnace which I have devised by supporting the ware upon a series of driven rolls such as are employed in an annealing furnace of the roller hearth type. As shown by the drawing each article of ware I2 is mounted on a carriage I3 which is supported on the rolls I4, the rolls being shown provided with the flanges I5 to properly guide the carriages, The rolls I4 as in a. roller hearth furnace construction extend substantially through the furnace walls and have reduced ends mounted in suitable bearings arranged at the exterior of the sheet metal casing 3 of the furnace. The bearings iii at one side of the furnace have their outer ends closed forming gas tight caps which by engaging the casing 3 prevent the loss of any gas atmosphere that may be employed in the chambers of the furnace. At the opposite side of the furnace the reduced ends of the rollers extend through the bearings i l and have sprockets it mounted therelon which are driven at a uniform rate by the endless chain le. 'I'o prevent the loss of a gas atmosphere through the bearings lll separate stuing boxes may be used at each bearing but preferably an entire row of bearings together with the adjacent sprockets and the cooperating chain are enclosed by a gas tight casing represented at 2t thus avoiding the necessity of using separate stufling boxes for the individual rolls. This casing construction forms no part of my present invention but is described and claimed in the copending application of George W. Hegel, Serial No. 94,380, led Aug. 5, 1936, and assigned to the same assignee as my present invention, which has become Patent 2,082,628.

Both chambers of the central section A of the furnace are provided with electric heating means represented diagrammatically by the heaters 22 which, as shown in Fig. 3, may comprise heating units arranged on the side walls and on the floor of the chambers, those in the latter position being covered by the protective plate 23. The heaters are connected with a suitable source of current supply through controlling devices, not shown, whereby the desired temperatures may be obtained in the various portions of the central section. Y

After the entering ware has been preheated in one of the sections B it passes on into the first portion of section A where its temperature is raised while still in air to a point slightly below that at which the enamel on the ware will fuse, for example 1000 F. Due to the arrangement of the heating units the ware is held at approximately this temperature for a certain length of time, for example seven minutes, to cause van oxidation of the steel beneath the coating of enamel. The ware in continuing its movement passes on over the peak of the furnacel into the second portion of the section A which contains a non-oxidizing gas atmosphere and in which a firing temperature, for example of 1580 F., is produced. From there it passes on into the other section B where it is allowed to cool in the presence of an air atmosphere while giving up heat to incoming cool ware in the other chamber.

It is well known to those skilled in the art that for good results enameled ware should not be jarred while the enamel is in a fused condition. In the furnace which I have devised, therefore, care has been taken to avoid jarring the Ware :at such a time by so arranging the heating means that the temperature of the ware, although raised to nearly the fusing point of the enamel on the upward incline, does not actually reach that point until after the ware has passed the peak of the furnace where due to the change in the path posite to the inlet pipes are the two air outlet pipes 28 and 2S. Each of the outlet pipes 26, 2, 28 and 29 is provided with a valve or damper Si) by 'which the flow of air or gas therethrough can be regulated. The gas inlet pipes 2t and 25 preferably are likewise provided with the valves or dampers 3l by which the flow of gas into the furnace may be regulated.

Inasmuch as the chambers of the furnace are inclined upwardlly toward thecentral point or peak of the furnace, the hot gasand air in the chambers will naturally tend to iiow toward that point. By regulating the dampers 3@ in the air and gas outlet pipes one may divide the gas from the air in each chamber at the middle of the furnace to prevent either one from mixing with the other in that portion of the chamber where it is not desired. By regulating the valves 3l in the inlet pipes gas may be supplied at the exact rate needed to prevent air passing up into section A or to prevent gas passing down into section B. The dampers in the outlet pipes also serve to regulate the speed at which the air is drawn into the open ends of the furnace. The gas and air outlet pipes may discharge directly into the atmosphere or if preferred may connect with a stack or with the intake side of a suitable blower.

While I have shown the furnace provided with separate gas and air outlet pipes at the central portion thereof, under certain circumstances I may prefer to employ a single outlet pipe for each chamber, a suitable division of the gas and air atmospheres being effected by the dampers in the outlet pipes in cooperation with the dampers in the gas inlet pipes.

For the sake of simplicity I have not shown any means by which the ware may be loaded on the rolls and unloaded therefrom, such means being -well 'known and forming no part of my present invention.

I have chosen the particular embodiment described above as illustrative of my invention and it will be apparent that various modifications may be made without departing from the spirit and scope of my invention ,which modifications I aim to cover by the appended claims.

What I claim as new and desire to secure by Letters Patent of the United States, is:

1. A furnace having a heat transfer' section comprising superposed chambers, means for supporting and moving material therein having different temperatures in the different chambers and a baille separating said chambers comprising spaced horizontal plates and a plate spaced vertically therefrom and overlapping said plates for preventing dirt from falling from the upper chamber into .the lower chamber but providing a free passage for the exchange of the atmosphere in said chambers.

2. An enameling furnace having a heat transfer section comprising superposed chambers, a series of rollers in each of said chambers for supporting and moving enameled ware, the ware in one chamber being at a higher temperature than that in the other chamber, and means comprising a plurality of vertically spaced overlapping plates for separating said chambers, and for providing a free exchange of the atmosphere in said chambers, said plates preventing the falling of dirt from the upper chamber on the ware in the lower chamber.

3. An enameling furnace comprising an elongated chamber having means for supplying heat thereto and having means for continuously moving enameled ware therethrough in one direction, said chamber having one portion containing an air atmosphere and inclined upwardly to an intermediate point and an adjacent portion containing a nonoxidizing gas atmosphere inclined downwardly from said point, means for supplying said gas to said adjacent portion and means adjacent said point for withdrawing air and gas simultaneously from said chamber, thereby determining the point of division between the air and the gas atmospheres.

4. An enameling furnace having means for supporting enameled ware therein and for moving it therethrough continuously, one part of the path of movement of the Ware in the furnace being inclined to another Vpart thereof, said other part being straight,whereby the ware is subject to jar in passing the junction of said parts, heating means for raising the temperature of the ware approaching lsaid junction to a point below the fusing temperature of the enamel thereon and heating means for increasing the temperature 'of the Ware beyond said junction on one portion of said straight part to effect the fusing of the enamel, said ware being cooled below the fusing temperature on another portion of said straight part.

5. An enameling furnace having a heating chamber provided with a series of rolls upon which enameled ware is moved through the chamber, one part of said chamber being straight and inclined downwardly from an intermediate point therein, means for heating the ware approaching said point to a temperature insufficient to fuse the enamel thereon, means for raising the temperature of said Ware beyond said point and in the higher portion of said inclined part to cause the enamel to fuse, and means by which said ware is cooled in a subsequent portion of said inclined part.

6. An enameling furnace having an elongated heating chamber, portions of which incline doWn- Wardly from an intermediate peak, a series of driven rolls in said chamber by which enameled Ware is moved continuously therethrough, means in said chamber for heating the ware approaching said peak to a temperature insufficient to fuse the enamel thereon, means for raising the ternperature of the ware after passing said peak to cause the enamel to fuse, the ware beyond said last mentioned heating means becoming cooled below the fusing temperature of the enamel thereon, and the rolls supporting the ware where -the enamel is fused providing a path substantially free of sudden changes in direction.

JAMES L. MCFARLAND. 

